1. Field of the Invention
This invention is directed to a method of accessing one or more optical fiber ribbons at an intermediate point along a length of optical fiber ribbon cable, and more particularly to managing the excess ribbon length at the access point.
2. Technical Background
Communication networks are used to transport a variety of signals such as voice, video, data transmission, and the like. Traditional communication networks use copper wires in cables for transporting information and data. However, copper cables have drawbacks because they are large, heavy, and can only transmit a relatively limited amount of data with a reasonable cable diameter. Consequently, optical fiber cables replaced most of the copper cables in long-haul communication network links, thereby providing greater bandwidth capacity for long-haul links. Still, most communication networks still use copper cables for distribution and/or drop links on the subscriber side of the central office. In other words, subscribers have a limited amount of available bandwidth due to the constraints of copper cables in the communication network. Stated another way, the copper cables are a bottleneck that inhibit the subscriber from fully utilizing the relatively high-bandwidth capacity of the optical fiber long-hauls links.
As optical fibers are deployed deeper into communication networks, subscribers will have access to increased bandwidth. But certain obstacles exist that make it challenging and/or expensive to distribute optical fibers toward the subscriber from fiber optic cables.
Optical fiber cables should at once have small cross sections, be light, and yet provide maximum protection to the optical fibers housed within. An optical fiber ribbon comprises a plurality of optical fibers bonded together, generally in a planar arrangement, and provides a cost effective way to obtain a high optical fiber density within a given cable structure. Cables may contain one or more optical fiber ribbons, usually divided into one or more stacks of many individual ribbons, and may have total fiber counts that extend into the thousands of fibers.
Optical fiber cables stretch under load, and similar to their loose fiber counterparts, ribbon cables may be manufactured in a manner such that a total length of a given ribbon is longer than the total cable length. The ribbon length that exceeds the cable length is referred to as the “excess ribbon length”, and its presence allows, inter alia, for stretching of the cable without severely straining the optical fibers within. Undue strain may cause the optical fibers comprising the ribbons to exceed their breaking stress.
From time to time there may be a need to access an optical fiber/optical fiber ribbon at an intermediate point between the cable ends, a process commonly referred to as mid-span access. For example, there may be a need to reroute an individual optical fiber ribbon, or one or more individual optical fibers that comprise a ribbon, in a direction that varies from the routing direction of the remainder of the ribbons in the cable. This is especially true in a distribution cable. Common names for this process include “breakout” or “furcation” (e.g. bifurcation), or a “tap”. That is, mid-span access may be necessary to tap into a cable and produce further, separate routing for portions of the original cable. These further separate routings, are variously referred to as “drop” cables or tether cables.
Mid-span access requires that the sheath or jacket surrounding the internal cable structure, and other intervening interior cable structure, be removed or otherwise opened to allow access to the optical fibers ribbons within the cable. A common problem encountered during a mid-span access operation is that once the cable has been breached, the excess ribbon length causes the optical fiber ribbons to spring out from the opened cable structure. Reconstituting the cable after the splice has been completed is thus problematic—it can be quite difficult to re-insert the ribbon, thus released, into the cable. Another problem that may be encountered is repairing a severed strength member during a mid-span access. As can be imagined, these tasks are difficult under the best of conditions, therefore the manufacture of preteiminated cables having the requisite number of taps is often undertaken in a factory setting. Still, the above difficulties must be overcome.